PROJECT SUMMARY/ABSTRACT Adults with hearing loss are more vulnerable to interference from background noise than adults with normal hearing. Despite the fact that the ability to extract speech information imbedded in background noise requires decoding differences in level across frequency (spectral information), few studies have addressed the extent to which we can provide spectral information to listeners with hearing loss. This fundamental gap in our knowledge prevents us from effectively addressing the systemic effects of hearing loss on communication, income, and ability to socialize with others. This work is a new application of established methods of characterizing spectral resolution to that of the most common device for rehabilitation of hearing loss?hearing-aid amplification. The proposed experiments will examine the degree to which access to spectral information can be restored to adults with hearing loss and the feasibility of utilizing this information to decrease interference from background noise. Aim 1 will delineate the impact of hearing-aid amplification on spectral decoding. Technology options that must be set by the clinician or hearing-aid manufacturer will be examined, including the frequency-specific gain, compressor speed, and number of compression channels. The proposed experiments will test the hypothesis that restoration of the lost dynamic range of hearing can support the encoding of spectral information. It is also hypothesized that the combination of technology options that best restore access to spectral information will differ across individuals and that these differences across individuals can be partially accounted for by an estimate of outer hair cell function. Aim 2 will determine the extent to which restoring access to spectral information supports speech recognition in background noise, under the guiding hypothesis that improving spectral resolution increases speech understanding. If it can be demonstrated that measures of spectral resolution with the provision of amplification are useful at delineating those who stand to benefit from different technology options, the knowledge gained could then be applied to the clinic to allow for clinicians to more successfully choose among different rehabilitation options.